The planar continuous transverse stub (CTS) antenna and antenna array were originally invented and patented by Raytheon in the early 1990's, for example, in U.S. Pat. No. 5,266,961, by W. W. Milroy, issued 29 Aug. 1991, entitled “Continuous transverse stub (CTS) element devices and methods of making same”. Benefits of the CTS antenna include compact size, lightweight, low cost, increased directive gain with increased radiating elements, and high efficiencies. The CTS antenna finds applications in the areas of mobile wireless and satellite communications and various military radar systems operating in the 500 MHz to 90 GHz frequency band.
A new coaxial version of the CTS technology with omni-directional radiation pattern is described in M. F. Iskander, Z. Zhang, Z. Yun, and R. Isom, “Coaxial Continuous Transverse Stub (CTS) Array,” IEEE Microwave and Wireless Components Letters, vol. 11, no. 12, pp. 489–491, 2001, and in U.S. Pat. No. 6,201,509, of inventors in common herewith. A coaxial version of the CTS technology for multiband operation was reported in R. Isom, M. F. Iskander, Z. Yun, Z. Zhang, “Design and Development of Multiband Coaxial Continuous Transverse Stub (CTS) Antenna Arrays,” IEEE Trans. Antennas and Prop., vol. 52, no. 8, August 2004. In particular, it was demonstrated that multiband performance at the 4.2 and 19.4 GHz frequency band with equivalent radiated power (˜98%) and good impedance match is possible to achieve using this technology.
However, it is deemed desirable to improve the CTS antenna to be flat-mounted and have a broadside radiation pattern, low fabrication cost, simple coaxial, coplanar, or microstrip transmission line feed, and simple integration with microstrip circuitry in a transceiver front-end. With the flat implementation of the design, it is possible to provide beam steering capabilities through the integration of the antenna structure with a tunable dielectric substrate material as will be described in more details herein.